1. Field of the Invention
The invention relates to a method and circuit for calibrating inductance and capacitance, and more particularly, to a method and circuit for calibrating inductance and capacitance by using an image rejection filter to compensate for process variations.
2. Description of the Related Art
Passive components that are used in Radio Frequency (RF) Integrated Circuits (ICs) typically have relatively large process variations. This leads to a direct trade-off between the accuracy of the resonant or resonance frequency and the bandwidth of the circuit.
As a result it is common practice to use relatively low-quality (or called low-Q) resonators in the RF signal path in order to ensure a sufficiently wide bandwidth and, thus, sufficient performance without requiring calibration.
However, the method as described above is not suitable for low bandwidth applications. For example, in the fields of global positioning system (GPS) or Bluetooth communications, because the system operation bandwidth is small, a low bandwidth amplifier is used. Therefore, in low bandwidth applications, high-quality designs are adopted to suppress the out-band spur while achieving low power consumption at the same time.
Accordingly, in low bandwidth systems, a novel method and circuit for calibrating inductance and capacitance to accurately detect the frequency drift caused by process variations and effectively calibrate the inductance and capacitances so as to compensate for the frequency drift caused by process variations are highly required.